Blank holddown apparatus



May 13, 1958 R. A. LABOMBARDE 2,334,262

BLANK HOLDDOWN APPARATUS Filed A ril 26, 1956 73 lIIIlI". 55 60 mm 7 7 2,4 50 40 41 44 "@EZ ih 'ipys 43 IN V EN TOR.

L RAWQIVD A. LABOMBARDE Taiwan P ATTORNEYS United States Patent 9 2,834,262 I BLANK HOLDDOWN APPARATUS Raymond A. Labombarde, Nashua, N. H. Application April 26, 1956, Serial No. 580,946 7 Claims. (CI. 93-49) This invention relates to an improved holddown apparatus for holding down leading overfolded portions and trailing unfolded portions of a plurality of box blanks advancing individually and successively through the adhesive applying zone of box folding machines of a well known type.

In paper box folding machines, of this type, the box blanks are individually fed from a magazine to conveyors and are advanced successively by the conveyors usually along a horizontal paper line through flap folding zones wherein the articulated portions of the blanks are prefolded into condition for glueing. It is necessary to hold the overfolded flaps and tabs in overfolded position as they travel along the paper line and holddown bars of rigid material are sometimes provided at fixed heights along the path of the blanks for the purpose. Such rigid, fixed holddown bars must be fixed, however, at the height of the thickest part of the blank passing thereunder, for example if holding down an overfolded flap the bar is set at double the thickness of the blank and if holding dowtn an overfolded flap having an overfolded tab the bar is set at triple the thickness of the blank.

It will be apparent that rigid holddown bars such as described above are thus in contact only with the highest face of a folded blank and that consequently the lower faces of the blank such as the main body are free to rise to the level of the underface of the bar. The blanks having an overfolded flap, or an overfolded flap and tab, pass through the adhesive applying zone of such machines and pass through the nip of a pair of adhesive applying rolls to enable a coating of adhesive to be applied to the upward facing glue flaps or tabs. The unfolded portions of the blank which are not held down flatwise, and upon which a coating of adhesive is undesirable, may rise upwardly due to many causes and come in contact with an adhesive roll thereby creating a commercially unacceptable box.

In the prior art leaf springs, spring mounted rolls, and the like have been proposed for yieldably holding down box blanks, but the high speed of untimed folding machines such as thirty or forty thousand blanks per hour, or five hundred to six hundred blanks per minute, tends to disadvantageously affect the operation of such devices. Five or six hundred double or triple thick portions of short, closely spaced blanks repeatedly striking a leaf spring or a spring roller within a minute may require the springs to be excessively strong to perform their function and therefore cause the holddown device to fracture the blanks in dropping from a high level to a lower level thereon.

Furthermore a roller presents a barrier to a rapidly advancing blank which tends to crumple or fracture the same because of the weight of the roller. The light weight, narrow-faced holddown element of this invention does not injure the blanks and engages only a small strip of the flap or tab being glued thereby permitting the remainder of the flap or tab to be covered with a wide strip of adhesive.

2,834,262 Patented May 13, 195$ 2 It is the principal object of this invention to provide a vertically movable holddown element alongside the nip area of adhesive applying rolls arranged to rockably yield to the passage of a thick portion of a rapidly advancing blank while holding down the thinner portions thereof without damaging the blanks.

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Another object of the invention is to provide a unitary, straight, holddown element of rigid material extending from well in advance to well in rear of the nip of adhesive applying rolls in a folding machine and arranged to not only yieldably rise over an overfolded flap passing at high speed thereunder but to rock on an axis in advance ofthe roll nip.

A further object of the invention is to provide an improved, vertically movable holddown element having a single, elongated, narrow, straight blank-engaging face spring pressed independently at both its forward end and its rearward end toward the path of an overfolded flap and away from an adjacent adhesive applying roll.

Other objects and advantages of the apparatus of the invention will be evident from the claims, the description of the drawing and from the drawing in which Fig. l is a side elevation, partly in section of the adhesive applying zone of a high speed box folding machine showing a blank with a leading overfolded flap and tab held down in accordance with this invention as the flap passes through the nip of the rolls.

7 Fig. 2 is a view similar to Fig. 1 showing the holddown element rocked downwardly at its rearward end into contact with the trailing portion of the blank.

Fig. 3 is a view similar to Figs. 1 and 2 showing one blank leaving the nip of the rolls with the succeeding blank arriving at the forward-end of the holddown element and Fig. 4 is an end view in section on and 2.

As shown in the drawing, the bar 20 represents one of the longitudinally extending supports of a typical paper box folding machine 21 and the upper face 22 thereof is the horizontal paper line of the machine. The foldable sheets or blanks 23, are fed individually and successively from a magazine and carried along the paper line of the machine by belts or chains, usually in untimed relation, through suitable folding apparatus which overfolds the flaps and tabs of the blanks into condition for coating with adhesive in the adhesive applying zone 24 of the machine. After the application of adhesive a final fold is made in a line 4-4 of Figs. 1

subsequent folding zone to create a collapsed, or other type box, from each successive blank. The feeding and folding mechanisms of such machines may be of any well known type and since they form no part of this invention, only the adhesive applying zone 24 is illustrated herein.

A pair of rolls 25 and 26 forming a nip 27, are provided in zone 24 for applying adhesive to the blanks advancing along the paper line in the direction of the Roll 25 is the pressure applying roll and roll 26 is the adhesive applying, or coating roll, of a glue pot of any well known type not shown, and roll 26 continuously applies a longitudinal strip of adhesive to the upper'face of such portions of a blank as are seized in the nip such as the triple thickness overfolded portion 28 of a blank 23 or of succeeding blanks'such as 29.

The holddown apparatus of the invention includes sup port means preferably in the form of a longitudinally extending holddown bar 35, of rigid material, having a flat straight lower face 36 parallel to, and spaced above, the paper line a distance equal to the triple thickness of blanks 23 formed by the blank main body 37, an overfolded flap 38 and an oppositely overfolded tab 39. The stationary, rigid, elongated holddown bar 35 may conveniently be mounted below the glue pot structure 40 nally from a point well in advance by machine screws 41 as shown and preferably its blank or flap engaging face 36 is comparatively wide as best shown in Fig. 4. The forward end 42 of bar is upturned and well in advance of the nip 27 while the rearward end 43 thereof is well in rear of nip 27. An elongated, side recess 44 is provided in bar 35 in the immediate zone of the nip 27 for a purpose to be explained hereafter. The support means also includes a pair of longitudinally spaced upstanding posts 45 and 46 fixed in bar 35, a block 47 vertically slideable on the posts, set screws such as 48 for adjusting the height of the block on the posts and a pair of longitudinally spaced, laterally projecting pins 49 and 50. Preferably also the support means includes a spacer projection 51, intermediate of the pins 49 and 50 and a side plate 52 substantially coextensive with block 47 and attached thereto by set screws 53 and 54. The plate 52, spacer projection 51, block 47 and recess 44 are arranged to form a vertical slot 55 at the forward end of block 47 and a vertical slot 56 at the rearward end of block 47, the pins 49 and 50 each extending across the central portion of their respective slots.

A holddown element 60, preferably of thin sheet material is provided, element 60 having a forward upstanding portion 61 slideable in slot 55 and a rearward upstanding portion 62 slideable in slot 56. Vertical slots such as 63 and 64 are provided in portions 61 and 62 to accommodate lateral pins 49 and 50 whereby the element 60 may rise and fall or rock in a vertical longitudinal plane as shown in Figs. 1-3. The intermediate portion of" element 60 between portions 61 and 62 is cut away as at 65 and a laterally extending flange or rim 66 is provided along the lower blank engaging face 67 of element 60. The forward end 68 of element 60 is upturned at an incline and the face 67 extends longitudiof nip 27, past the nip to a point well in rear thereof. It should be noted, however, that the centre of the element 60 is not at the nip 27 but rather is in advance of the nip. It should also be noted that because of the side recess 44 the element 60 is within the confines of the bar 35 to enable the lower face 67 to operate within the lateral limits of the bar with a comparatively narrow face such as formed by the flange 66.

First spring means 70 is provided between the forward end portion 61 and the adjacent forward end of the block 47 and second spring means 71 as provided between the rearward end portion 62 and the adjacent rearward end of the block 47, for urging the opposite ends of element 60 downwardly toward the paper line. Preferably spring means 76 and 71 are formed in a single bowed leaf spring 72 having its centre point 73 fixed to the block 47 by a set screw 74. Thus independent spring action is achieved at opposite ends of the element 60 by means of a single spring 72. The centre 73 of spring 72 at set screw 74 is in advance of nip 27 and the curved underfaces 75 and 76 of spring 72 are each in contact with the adjacent corner 77 or 78 of the upstanding forward and rearward portions of element 60.

In operation, the holddown bar 35 is fixed laterally close to and alongside the lateral position of the nip 27 to extend well in advance and well in rear of the nip at a height above the paper line equal to the height of the top face to be held down such as face 80 of the triple thick overfolded portion 23 of the blanks 23. The holddown element 6?) is then adjusted on its block 47 to yield upwardly from the level of the paper line to the level of the lower face 36 of bar 35 within the lateral confines of the bar. Element 66, in its recess 44, is longitudinally positioned to locate its rocking axis at 73 in advance of the nip 27, its forward end portion 61 and spring means 70 well in advance of the nip and its rearward end por tion 62 and spring means 71 in rear of the nip. Blanks such as 23 and 29 advancing at high speed in the direction of the arrows with the overfolded flaps and tabs 38 and 39 in the lead and the single thickness main body portion 37 trailing may have both the upper face 80 of the thick portion 28 and the upper face 81 of the portion 37 in contact with lower face 36 of bar 35. The face 81 may be in such contact because of natural curl of the paper stock, the effect of the feed mechanism, the effect of air currents at high speed or other reasons. In any case, upon reaching the adhesive applying zone 24 the thick blank portions 28 raise the forward end 61 of element 60 against spring pressure to triple height as shown in Fig. 3 while the rearward end 62 is riding the face 81 of the preceeding blank at single height. Upon reaching the centre point 73 of element 60, the forward, centre and rear of the element are raised to triple height, since the face 81 has passed the nip 27 and is in no dang-er of misapplication of adhesive. Upon passing the centre point 73 and reaching the immediate nip zone the rearward end 62 of element 60 remains at triple height while the forward end 61 well in advance of the nip 27, gradually rocks downward to press the trailing single thickness portion of the blanks flatwise down on the paper line as shown in Fig. l. The element 60 remains at single thickness height as shown in Fig. 2 until its forward end 61 is again raised by the next succeeding blank.

The thin sheet materialv of element 60 gives an extremely light weight thereto in view of the elongated flap-engaging face 67 thereof whereby the barrier effect and inertia of the element is at a minimum. As best shown in Fig. 4 the element 60 is preferably longitudinally aligned close to the adhesive applying roll 27 and engages only a narrow strip at the free end of an overfolded tab such as 39 whereby the roll 27 may coat the remaining major portion of the tab 39 with adhesive. The element 60, however, and the corresponding portion of the lower face 36 of bar 35 are sufficiently in contact with the overfolded tab and flap to prevent any inadvertent rise thereof which might cause misapplication of adhesive in the adhesive applying zone.

I claim:

1. Holddown apparatus for holding down portions of a foldable box blank, advancing individually and successively through the zone of an adhesive applying roll opposed by a pressure roll in a box folding machine, said apparatus comprising fixed, rigid, support means on said machine in said zone and proximate the path of said blank portions; a unitary, elongated, holddown element of rigid material mounted on said support means alongside the nip of said rolls for movement normal to the path of said blanks, said holddown element having a straight elongated holddown face normally parallel to said path and extending along said path from a forward end in advance of the nip of the rolls to a rearward end in rear of the nip of the rolls; first spring means between the forward end of said holddown element and said support means for resiliently urging said end in a direction away from the adhesive applying roll and toward the path of the flatwise unfolded portions of said blank and second spring means between the rearward end of said holddown element and said support means for resiliently urging said end in a direction away from the adhesive applying roll and toward the path of the fiatwise unfolded portions of said blank whereby said elongated holddown element rocks as it yields upwardly for holding down the unfolded part of a blank trailing behind an overfolded flap.

2. Apparatus as specified in claim 1, wherein said support means comprises an elongated, holddown bar parallel to, and spaced above the path of said blanks, said holddown element is located in an inwardly extending, elongated, side recess in said bar and said holddown element is supported for vertical movement on said bar by a forward lateral pin and vertical slot connection and a rearward lateral pin and vertical slot connection.

3. Apparatus as specified in claim 1 wherein said support means includes a forward and a rearward vertical slot, said holddown element includes a for-ward and a rearward upstanding portion slideable in said slots and projecting thereabove, and said first and second spring means comprise a single bowed leaf spring having its centre portion fixed to said support means and each opposite free end portion in spring pressure engagement with one of the portions of said holddown element projecting above said slots.

4. Apparatus as specified in claim 1 wherein said support means includes an elongated holddown bar having a forward and a rearward upstanding pin thereon, a block vertically adjustable on saidpins and having a forward and a rearward laterlly projecting pin and a side plate coextensive with said block but laterally spaced therefrom to form a vertical slot therebetween for slideably receiving said holddown element.

5. Holddown apparatus for holding down trailing portions of box blanks while overfolded leading portions are advanced through the nip formed by an adhesive applying roll and a pressure roll rotating on fixed axes in a box folding machine, said apparatus comprising support means proximate the path of said blanks alongside said adhesive applying roll; a unitary, rigid light weight holddown element mounted for vertical and rocking movement on said support means and having a holddown face extending from well in advance of said roll nip to well in rear thereof and a unitary, bowed leaf spring centrally fixed to said support means and substantially coextensive longitudinally with said holddown element, said spring having a forward and a rearward free end, each resiliently urging the adjacent end of said holddown element away from the coating face of said glue adhesive applying roll and toward the path of the flatwise unfolded portions of said blanks whereby said element rocks, as well as rises, upon passage thereunder of an overfolded flap to hold down the trailing unfolded portions of said blanks.

6. Apparatus as specified in claim 5 wherein said support means includes an elongated holddown bar having a fixed blank engaging face and the blank engaging face of said holddown element is within the confines of said bar and longitudinally aligned with the corresponding portion of said fixed blank engaging face.

7. Apparatus as specified in claim 5 wherein the rocking axis of said holddown element, located at the central point of said spring is in advance of the nip of said rolls whereby the forward end of said element rocks downwardly into contact with the trailing portion of a blank while a leading overfolded flap on said blank is passing through the nip of said rolls.

No references cited. 

